So your coach wont start.
My trouble shooting tools
A. A volt meter
B. A test light with long leads and alligator clips on end.
C. A alternate remote starts switch
D. A cheap or expensive battery load cell capable of loading a 100 amps or more
E. Battery charger
F. Necessary tools and cleaning supplies
Start with the simple things first, order you follow is up to you, however I generally follow the following.
A. Volt meter . Check the voltage at the suspect battery
1. If its dead charge and check capacity. If it fully charges fast it probably will have capacity issues. Check with load cell.
If its fully charged check voltage at starter main connection
A if you have full voltage using alternate start control engage starter
Does starter solenoid engage?
Yes? Check solenoid start wire for power during start attempt. Repair wiring.
No? But have voltage, on both big lead and start solenoid wire, bad starter solenoid
Solenoid engages but no start bad solenoid or starter.
B no Voltage at starter? But good battery voltage.
Using volt meter or 12V test bulb put one lead on the center of the battery positive post and the other at the terminating end of the cable on positive post.
If you read voltage or bulb lights up you have isolated your problem to that lead.
Repeat on the other battery cable ground but this time go to coach ground on the frame somewhere.
If you read voltage or bulb lights up you have isolated your problem to that lead.
Using load cell on batteries and at termination connection post and at cable splice locations will isolate fault. Sometimes voltage will be present but drops off during a load.
Typical issues will be connections and failed batteries.
Using the test bulb and remote start switch along (parrellel) long leads quickly isolates problems. Can also be used along (parrellel) positive or negative battery connections to see resistance. Cleaning connections and protecting from the air reduces corrosion. Preventive maintenance does take time but prevents on the road issues. I'd rather change a starter at home at my time schedule rather than in the fuel line at the pumps.
If all checks out verify good starter to ground connection, using test bulb or volt meter. I personally do like the bulb do to visual indication on leads and between battery leads. If it lights up there is an issue, remember to verify it works before using. This also works across bad boost switches and Isolators, but not mentioned here because they do not affect starting issues. Poor capacity batteries may need boost to start, but this should not be the normal starting procedure. If you must use boost to start you are covering up other issues, Batteries, leads, connections. Hope this is helpful. Anything that should be added let me know and I'll add to the list.
Test light I use is just a plain 12v brake light bulb with wire leads soldered to bulb base. Tape to cover. Alligator clips on the end of the wires.
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Scott
Good test plan Scott. Just a cpl of comments. I would recommend a smaller test bulb for better sensitivity.
SYLVANIA 3893 Basic Miniature Bulb, (Contains 10 Bulbs)
SYLVANIA 3893 Basic Miniature Bulb, (Contains 10 Bulbs) (https://a.co/d/h0RXLDH)
Also, when testing with the bulb be sure to draw some current across the terminal. Turn on headlights, dash fan on high, etc, or try to start engine.
Here is a good deal on an Auto Meter load tester. I have refurbished 2 of these off eBay, replacement meters are available from Auto Meter. This one appears to just need oiling the fan.
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Yes will help if all loads are at end of the fault circuit. Cheap load tester will also induce enough to locate resistance very nicely. I absolutely agree on the bigger is better load cells 800 amps( use mine all the time) but the resistance cheap ones do a great job and can travel with the coach easily. Difficult to see the unseen. Gauges for pressure/vacuum and volt/load capability for power. Having a cheap one is way better than nothing. Also is a functional volt meter although clunky. For 30$
Scott, I coudn't start my coach, yesterday, even with the booster switch. Starter batteries are about two years old and new coach batteries. Put a charger on the start batteries and she fired up today. What would cause the start batteries to lose their charge just sitting around for two weeks?
The start batteries have some small drains,research the trickle chargers,keep one on mine most all the time,the better ones will
desulphate your battery so it lasts longer,if your batteries are AGM you need a charger specifically designed for those batteries.
When the Coach has not been started or run in a while and motor is cold, Touch the alternator. If warm or warmer then the engine, good chance Diodes have gone bad. If you have an isolator, also check that to see if warmer then the engine, or other item around it..
Good Scott. What if you break it into some sections? Your thread could cover #1 and #2 below. For #3, you could have a fuel issue, bad CPS, etc. which is another potentially longer topic. Or the title of the topic could be changed too - Coach wont start trouble shooting (battery).
1) turn the key and nothing (completely dead)
2) turning over slowly
3) turns fine but no start.
So many different fuel systems and engines to consider. Rather group into small sections. Batteries are much more simple and diagnostic equipment cross over to all other equipment with batteries. Point being diagnostic equipment is needed for each and every repair group. Yes I was only referencing battery, state of charge, cables and starter issues seems everyone goes threw eventually.